1. Field of the Invention
This is a continuation of Application Ser. No. 866,579, filed May 22, 1986 now abandoned.
This invention relates to an apparatus for detecting ophthalmic diseases in the lens of a patient's eye, and more particularly to an apparatus for detecting ophthalmic diseases by irradiating a laser beam via an optical system at one spot in the interior of a patient's eye, and by detecting the laser light back-scattered therefrom.
2. Description of the Prior Art
Cataracts are a common ophthalmic disease in which protein particles normally found in human crystalline lenses increase in size, thereby causing turbidity in the lens. Measuring the size and diameter of these protein particles is essential to effecting early detection of a cataract condition and to preparing preventative medical treatment thereof.
A human eye comprises transparent elements such as a cornea, crystalline lens, etc. Fine protein particles are contained in these transparent elements and exhibit Brownian movement. In normal disease-free eyes, the protein particles are distributed in the form of small diameter particles, however, in turbid eyes, the particles are of a larger diameter.
There is known in the art an apparatus for measuring the diameter of protein particles in the human eye, which comprises a laser for generating and then imaging a laser beam on a selected portion of the crystalline lens of the eye of a patient to be measured. Protein particles exhibiting Brownian movement travels through the portion of the lens of the eye on which the laser beam is focussed to cause the backscattering of the laser beam. Part of the laser light back-scattered in this manner is directed toward the eyepiece of a binocular microscope for monitoring, and another part thereof is directed toward a photomultiplier which converts the intensity of the back-scattered light into an electrical signal. This signal is input to an autocorrelator which determines an autocorrelation function with resepct to the fluctuation of the intensity of the back-scattered beam over time. The thus obtained correlation value is then used to calculate the relaxation time of the fluctuation of the intensity of the back-scattered beam. Accordingly, a diffusion coefficient can be further derived based thereon which may then be used to determine the diameter of the protein particles.
According to a prior art ophthalmic disease detection apparatus of this type, previously the control of luminous energy emitted from the laser light source and from a slit light source, and the manipulating of the OFF/ON of the shutter of a photomultiplier used to measure the intensity of the scattered light have been performed mechanically by hand, hence there has been a problem relating to the amount of time required in measuring.